Field of the Invention
This invention relates generally to intraocular lenses and intraocular lens systems, and more specifically to deformable intraocular lenses and lens systems for providing accommodation.
Description of the Related Art
Monofocal intraocular lenses are now commonly used to restore vision lost, for example, due to the formation of cataracts. More recent efforts in the field have concentrated on restoring or simulating accommodation, the ability of the eye to provide both near vision and distant vision. One approach to providing accommodation for an eye in which the natural lens has been removed is to use a bifocal or multifocal lens that simultaneously produces two or more foci. For example, a refractive lens surface may be produced in which different portions of the surface have different focal lengths, for example, as taught by Portney in U.S. Pat. No. 5,225,858. Alternatively, Cohen teaches in U.S. Pat. No. 5,121,979, the use of a bifocal lens comprising a diffractive phase plate in which the entire lens produces two different foci corresponding to two different diffractive orders. Bifocal lenses utilize the ability of a subject's brain to give preference to the focus corresponding to a selected image.
Another approach is to provide an intraocular lens that is directly responsive to the ciliary muscle of the eye. For example, in U.S. Pat. No. 6,551,354, an intraocular lens is used to produce accommodation by providing an optic that moves in the anterior direction when the ciliary muscle contracts. In U.S. Pat. No. 6,616,692, herein incorporated by reference, a first optic having a negative optical power is combined with a second optic having a higher optical power than the first optic. The combination of the first and second optic advantageously reduces the amount of axial movement in the eye needed to provide accommodation for intermediate and near vision.
In another approach, accommodation is provided by using ciliary muscle contraction to deform at least a portion of the intraocular lens optic. One potential problem with this approach is that the shape of the optic surface produced during accommodation may result in undesirable amounts of optical aberrations, for example, spherical aberrations.
Accommodating intraocular lenses are needed that easily and effectively deform and change shape to provide both distant vision and near vision in a way that provides design flexibility and/or reduces optical aberrations.